1. Field of the Invention
The invention relates to a lettering device having a keyboard portion for selecting the symbols to be written and a writing portion, optionally separate from the keyboard portion, which has a writing arm. The writing arm receives a stylus and is movable between a position of repose and a writing position. The writing arm is movable along cartesian coordinates by means of two motors, which are driven in accordance with the symbol to be written. The motors are disposed stationary relative to the coordinate origin, and the writing arm is secured such that it is movable in the direction of one coordinate on a guide rail that in turn is movable by the first motor in the direction of the other coordinate and such that it is movable in the direction of the other coordinate on a second guide rail that in turn is movable in the direction of the first coordinate by the second motor. The writing arm has a guide slit extending in the direction of its longitudinal extension and in the direction of the first guide rail, in which a guide bearing is guided, which is coupled to a stationary runner rail extending parallel to the second guide rail.
2. Brief Description of the Prior Art
In a known lettering device of this type (German Utility Model DE-GM No. 79 16 714 or U.S. Pat. No. 4,356,632), which is also produced and sold by rotring-werke Riepe KG under the name "NC-scriber"), a lowering strip extending parallel to the runner rail, and also parallel to the second guide rail, extends underneath the writing arm at least over the entire region transversed by the writing arm. This lowering strip, in its position of repose, keeps the writing arm in this position of repose and can be lowered by means of a lifting magnet so that the writing arm then drops into the writing position, by its own weight.
Aside from the fact that the displacement movements of the lowering strip are noisy, movement of the lowering strip requires a relatively great expenditure of energy, since its massive design makes the lowering strip relatively heavy. Because of the attendant inertia, the speed of the lowering and raising movement of the lowering strip is also relatively low, which can limit the writing or drafting speed.